Process for fireproofing wood, and products therefrom



Patented Nov. 30, 1937 UNITED STATES PATENT OFFIE PROCESS FOR FIREPROOFING- WOOD, AND PRODUCTS THEREFROM No Drawing. Application August 24, 1936, Serial No. 97,594

2 Claims.

This invention relates to the process of fireproofing wood and lumber, and to the products of such process. In the building and construction of houses, and other structures and parts 5 thereof, it is important that the materials used therefor should be fire resistant, and fireproof. Heretofore one objection to the use of lumber for all of such purposes, has been the danger of loss thereof by fire, and injury to persons and property from such fires.

Heretofore attempts have been made to render woods, and lumber and particularly Wood compositions, fireproof, generally by subjecting such products or material to a series of immersions into solutions of water and chemicals. Such chemical solutions have sometimes contained a percentage of ammonium chloride, with other chemicals designed to aid in the penetration thereof or to prevent the escape of such ammonium chloride.

Such immersions have ordinarily been required under a pressure and generally under a vacuum pressure, to insure any sufficient or material degree of penetration and such immersions have ordinarily been alternated with a drying of the woods. Attempts have also been made to prevent the escape of such fireproof materials by the evaporation of such chemicals when only near the surface by the use of soaps for sealing the outside pores of the wood, and such methods have ordinarily changed the color of the woods so treated and frequently imparted to the same, disagreeable odors. All such methods have resulted in but slight penetration of the woods treated, generally less than one sixteenth of an inch, and

frequently not over one sixty-fourth of an inch beneath the surface treated. The use of all heretofore known methods have been also complicated and costly, thereby necessitating a higher price to be demanded for such treated material,

0 and so creating difiiculty in competition with the sales of other woods not treated, and preventing a commercial success.

It is therefore an object of this invention to provide a process whereby all such wood and lumber materials may be rendered impervious to fire, and loss thereby, by the subjection of such wood and materials to a solution of suitable chemicals and the impregnation of such wood and materials to a suitable depth by such chemicals.

It is therefore a further object of this invention, to provide a simple and inexpensive method of fireproofing natural woods, by a single immersion of such woods into a fireproofing solution and without successively drying or soaking the same, whereby such fireproof condition will be tances to render the same fireproof.

A still further object is to provide a manufacture comprising wood and lumber with the surfaces and interiors thereof impregnated with such chemicals, and particularly with such sal ammoniac, for the desired depths, and rendered fire- 15 proof thereby.

The process comprises, the dissolving of such sal ammoniac of the proportions of approximately 1 pound of 16 ounces to one gallon of water, and adding thereto 2 fluid ounces of acetic acid 99 per cent pure, heating the same to approximately Fahrenheit, and immersing the wood to be treated in such solution, and maintaining the same so immersed under such heat for sufiicient period of time to cause such solution to penetrate such wood a desired distance therein, then drying such wood to be ready for use for any purpose.

Woods of different degrees of hardness, and variations of grains, require different periods of time for proper treatment, as hard woods, and woods with close or fine grains, ordinarily require longer periods of treatment than do soft woods and woods of open grains, for the same degrees of penetration. And in some cases of unusually hard woods, the proportions of the sal ammoniac and acetic acid, may be increased to expedite the periods required for a desired degree of penetration and impregnation.

In practice with such process on Douglas fir 40 wood and lumber, a medium soft wood, the following periods of time have been found sufiicient to impregnate such lumber the following distances respectively. Three hours one quarter of one inch; three and half hours, three eighths of 45 one inch; four hours one half of one inch; six hours, one inch; and other distances in approximately same proportions. Such periods of time for like proportions of impregnation, both approximately, are substantially basic for medium 5() soft woods, with heat maintained at from 190 to 200 Fahrenheit.

In. commercial practice it is advisable to construct vats or tanks of sufiicient capacity to treat a given quantity of such wood or lumber at one 55 time, then fill such receptacles with sufficient of such solution of approximately the proportions named, of the desired heat or temperature, then immerse such Wood or lumber in such solution, and maintain such heat by furnaces or steam, the desired periods of time for the desired penetration, then remove such wood or lumber and dry the same in suitable kilns, or in the open air. Wood and lumber so treated is found to be fire resistant and fireproof. All kinds of lumber and particularly plywoods, are successfully so treated.

After repeated experiments, we have found that by the use of acetic acid in solution with water and a fireproofing agent, particularly sal ammoniac (commonly called ammonium chloride) that such agent is carried by said acetic acid deeply into and below the surface, and the pores and cells filled, of any wood treated thereby, and that by the use of acetic acid in such solution, that it is unnecessary to apply such solution under vacuum. We have further found that wood so treated and thereafter dried, is not discolored but retains its natural appearance and without any unnatural odors. While we have described the application of the solutions to the wood, as under a comparatively high degree of heat, this is for the purpose of hastening the impregnation, and by a greater time exposure it is possible to obtain the desired impregnation without such heat, when acetic acid is used.

The process is particularly important for the fireproofing of laminated sheets of plywood with natural wood grains, for inside finish, for the prevention of fires. It is also valuable for treatment of natural lumber for general purposes, all of which is more difiicult to impregnate than pulp, or wood fibre.

Having described our invention we claim as new:

1. A process of fireproofing wood which consists in immersing the wood in a heated bath of an aqueous solution of ammonium chloride and acetic acid in the approximate proportions of 1 pound of ammonium chloride, 2 ounces of acetic acid and one gallon of water, and maintaining said immersion until the wood has been impregnated to a substantial depth.

2.. A process of fireproofing wood which consists in immersing the wood in a heated bath maintained at approximately to 200 Fahrenheit of an aqueous solution of ammonium chloride and acetic acid in the approximate proportions of 1 pound of ammonium chloride, 2 ounces of acetic acid and 1 gallon of water and maintaining said immersion until the wood has been impregnated to a substantial depth.

DANIEL F. MOORE. MAX A. WICKS. 

